How do we measure climate change?

Several methods can be used to observe climate and climate change. Today’s scientists use sophisticated instruments and satellites to measure climate parameters. We can also look back through time by studying ice cores and sediment cores that provide indirect evidence about past temperatures and other climate conditions. Climate change is measured both globally and regionally.

Ice sheets as climate archives

Glacier ice, particularly the ice in the inland ice sheets of Antarctica and Greenland, holds a treasure trove of information about climate in ancient times. The snow that once fell here contains information about ambient climate hundreds of millennia back in time. Tiny air bubbles trapped in the ice allow scientists to study how the composition of the atmosphere has changed with temperature over time.

One of the most important sources of information in these icy archives is cryptically called δ18O or dD. This is a measure of the relative concentration of different stable isotopes of oxygen in the water the ice crystals are made of. In simple terms, every time water evaporates from the ocean or falls as precipitation, the molecules of water (H2O) that contain certain stable isotopes are more likely to be involved. The exact fraction is temperature-dependent, so if we analyse the snow on the glaciers, we can create a time-line that tells us how temperatures in that area have varied. When this information is stored over long time spans, it becomes a climate archive.

As in all archives, accurate dating is important. Many different methods can be used to calculate the age of an ice core, and several are usually used in parallel. Horizons (layers) formed in conjunction with historic events are important in this context. Volcanic eruptions provide another important way of dating ice cores. Read more.

The most common climate observations are of temperature and precipitation. Other climate variables include humidity, wind speed and direction, air pressure, cloud cover and solar radiation.

In polar regions, observed changes in sea ice, snow cover and glaciers also tell us what is happening with the climate.

Climate change research at the Norwegian Polar Institute

The Norwegian Polar Institute conducts research on past climate and on present-day physical processes in the sea, in sea ice and in ice on land. In Antarctica, our scientists have helped procure information about climate in the past by drilling ice cores in the massive ice sheet of Dronning Maud Land. This ice, with its air bubbles, serves as a climate archive, “capturing” gases from the ancient atmosphere and providing information that goes back 900 000 years. In Fram Strait, we examine bottom water formation and sea ice, and in Svalbard we monitor the size (mass balance) of glaciers.

The Centre for Ice, Climate and Ecosystems (ICE), through its extensive research programme, provides knowledge about Arctic and Antarctic climate, and what effects climate conditions at the poles might have on the rest of the world.

Climate

Climate is weather averaged over a long time. To understand climate, one must observe weather over extended periods, so that isolated extreme weather situations do not influence the conclusions.

There are many ways to observe climate and climate change. The observations most frequently used are temperature and precipitation. Other climate variables of relevance include air humidity, wind speed, wind direction, air pressure, cloud cover, and solar radiation. In the Arctic, observations of snow and ice cover are crucial and can give us a picture of climate over long spans of time. This underlines the critical importance of long-term environmental monitoring.